Clown Prince's content: one with four siblings (9)

I believe the answer is:

harlequin

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'clown' is the definition.
(I know this)

'prince's content one with four siblings' is the wordplay.
'prince' becomes 'charles' (Prince Charles).
'content' says to take the centre.
'one with four siblings' becomes 'quin' (I can't explain this - if you can you should give a lot more credence to this answer).
The centre of 'charles' is 'harle'.
'harle'+'quin'='HARLEQUIN'

Can you help me to learn more?

(Other definitions for harlequin that I've seen before include "Spotted dog < with clown" , "Pantomime character in a tight spangled costume" , "Traditional pantomime character" , "Character in a diamond-patterned costume - variegated" , "Foppish lover of Columbine" .)

I've seen this clue in The Independent.

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